Evaporator control for absorption refrigeration systems



July 14, 1959 E. F. PALMATIER EVAPORATOR CONTROL FOR ABSORPTIONREFRIGERATION SYSTEMS 5 Sheets-Shet 1 Original Filed July 16, 1953 FIG.I-

INVENTOR. EVERETT P. PALMATIER ATTORNEY July 14, 1959 E. F. PALMATIER2,394,380

EVAPORATOR CONTROL FOR ABSORPTION REFRIGERATION SYSTEMS Qriginal FiledJuly 16, 1953 3 Sheets-Sheet 2 FIG. 3

IN V EN TOR.

EVERETT P. PALMATIER By I ATTORNEY July 14, 1959 E. F. PALMATIER 3Sheets-Sheet 3 Original Filed July 16, 1953 FIG. 4

IN VEN TOR. EVERETT E PALMATIER ATTORNEY EVAPORATOR CONTROL FORABSORPTION REFRIGERATION SYSTEMS Everett Perry Palmatier, Solvay, N,.Y.,assignor to Carrier Corporation, Syracuse, N.Y., a corporation ofDelaware Original application July '16, 1953, Serial No. 368,355.Divided and this application November 1, 1954, Serial No. 466,064

9 Claims. (Cl. 62-476) This application is a division of my copendingapplication Serial No. 368,355, filed July 16, 1953, entitled EvaporatorControl for Absorption Refrigeration Systems, and relates generally toabsorption refrigeration systems and more particularly to an arrangementfor maintaining a desired pattern of refrigerant feed within theevaporator of the system so that liquid refrigerant at a predeterminedrate is supplied to each tube of a multitube evaporator in such a manneras to ensure eflicient distribution of the liquid refrigerant in theevaporator.

One type of absorption refrigeration system with which this inventionmay be used has a capacity of about tons of refrigeration and may beemployed with appara tus forming a heating and cooling system for anenclosure such as a residential home. Flow of liquid refrigerant in thesystem is of a very small order, such as about a pint per minute. Undersuch circumstances it is important that the amount of liquid refrigerantflowing into the evaporator from the condenser, when the system isoperated to provide a cooling effect, be efiiciently utilized. Theparticular evaporator structure involved includes a plurality ofvertically spaced tubes connected at one end to an upper header and theother end to a lower header. Preferably the liquid refrigerant isintroduced into the upper header from where it flows downwardly throughthe tubes in a film and is vaporized therein as it absorbs heat from theair from the enclosure as the air ispassed over the evaporator unit by afan or the like.

The flow of liquid refrigerant, usually water, downwardly through thetubes is of a very small order depending, in addition to the ratementioned above, on the number of tubes forming the evaporator. In anyevent the amount of liquid flow in film form is so small that therefrigerant changes state in the evaporator through the phenomena ofsurface evaporation. It will be appreciated that those tubes in theentering air side of the evaporator will be in contact with the warmestair and the tubes lying downstream toward the leaving air side of theevaporator will each be subjected to cooler air. Therefore it isnecessary to vary the amount of refrigerant flowing in each tube inaccordance with the load as represented by the temperature of the airflowing over the tubes.

This invention is concerned with the adaptation to each tube of a devicefor regulating the flow of refrigerant to the tube in accordance withthe design rate, which rate is of course determined in accordance withthe conditions described above such as the position of the tube withrespect to the air flow, and amount of liquid refrigerant available fordistribution.

Accordingly, this invention has for its chief object the provision of adevice adapted to be applied to each tube of a multi-tube evaporatorunit for regulating the flow of liquid refrigerant to the tube.

A further object is the provision of a device of the kind underconsideration wherein the vapor produced within the tube, as an exchangeof heat occurs between the evaporator'and the air to be conditioned, isutilized to regulate the fiow of liquid refrigerant into the tubethereby preventing the tube from receiving an amount of refrigerant inexcess of that desired. 1

A still further object is the provision of a flow regulating devicewherein the vapor flow is controlled in such a manner as to store orcirculate within the upper header quantities of liquid refrigerant inexcess of that necessary to maintain the proper feed rate. I

The invention relates to an evaporator feed control device includingmeans to feed liquid refrigerant to the tube in desired amounts, thedevice being arranged so that vapor formed in the evaporator tube isused to regulate the supply of liquid to the tube. The desiredregulation is preferably accomplished by providing each tube with areceptacle formed with a liquid accommodating reservoir and a passagewayfor the flow of vapor from the tube, the passageway being arranged insuch a manner that the vapor flow therein induces a portion of theliquid in the reservoir to flow through a separate passage and beentrained in the vapor stream rather than to flow into the tube.

The invention also relates to a method of regulating the supply ofliquid refrigerant to the tube of an evaporator wherein vapor formedwithin the evaporator tube is used to assist in the regulation of thesupply. 7

Other objects and advantages of the invention will be apparent upon aconsideration of the ensuing description wherein one embodiment of theinvention is described, it being understood that the description is notto be considered as limiting the scope of the invention.

Figure 1 is a diagrammatic view of an absorption refrigeration systemincluding the present invention;

Figure 2 is a view partly in elevation and partly in section, of anevaporator unit equipped with the liquid flow regulating device of theinvention;

Figure 3 is a side view partly in elevation and partly in section,illustrating one form of the receptacle used tov unit 7 through lines 5and 8.

The term Weak solution is here employed to describe a solution of arefrigerant such as water and an absorbing salt such as lithium bromide,which solution is rich in refrigerant so that its absorbing propertiesmay be considered weak. The term strong solution here employed, refersto a solution, of the type described above,

deficient in refrigerant so that its absorbing properties may beconsidered strong.

From the heat exchange unit the solution flows through line 9 to thegenerator 4 where a part of the water is boiled off and passes in thevapor phase through line 9" to, the condenser 4'. Line permits strongsolution, remaining in the generator after thevaporous refrigerant haspassed to the condenser, to pass to the heat exchange unit where itwarms weak solution passing to the generator. Line 11 permits passage ofthe strong solution to the absorber 2 from the heat exchange unit 7.

The vaporous refrigerant passing to the condenser through line 9' ischanged to the liquid state through the action of a cooling coil and isthen forwarded to the evaporator 3 through line 12 which is providedwith a looped portion designed to provide pressure Thus a. two pressuresystem, wherein the evaporator and absorber are at one pressure and thegenerator and condenser at. a higher pressure, is provided. From theevaporator, vaporous refrigerant passes to the absorber tobe mixed withthe strong solution returning from the generator, the heat ofcondensation, in this instance, being absorbed by a cooling coil in theabsorber. After the strong solution is diluted as described, theresulting weak solution passes to the pump to complete the cycle. Acooling circuit including a coil in the condenser (not shown), line 16,a coil in the absorber (not shown), line 15, a cooling tower completewith pump (not shown) and line 17 from the cooling tower completes therefrigeration system.

The evaporator structure is shown in detail in Figure 2 wherein an upperheader 23 and a lower header 24 are in communication with each otherthrough a plurality of tubes 20 and a by-pass vapor line 28. Each tubeis shown with its upper end projecting above the bottom of the uppervapor header and a feed regulating device applied to the projecting end.A baffle 29 is shown for preventing flow of liquid refrigerant into thevapor bypass line. Each tube is provided on the inner surface thereofwith a series of circumferential grooves 26 for ensuring adequatedistribution of the liquid refrigerant over the inner surface of thetube. Pins 27 are assembled about the outer surface of the tube toassist in providing efficient heat transfer action. Liquid refrigerantenters the evaporator through line 12, and collects in the upper header.

In accordance with the invention, the amount of liquid feed necessary toprovide .a desired film of refrigerant on the inner surface of one ofthe tubes of the evaporator unit may be ascertained for a certain loadunder predeterrnined operating conditions.

The device shown in Figure 3 is arranged to regulate the flow of liquidrefrigerant from the upper header into the tube in the desired manner.Referring more particularly to the construction it will be noted that aregulating device of the type under consideration is applied to eachtube. Disposed about an evaporator tube 58 is a feedcontrol device 59,which has one or more feed holes or openings 60 spaced about the bottomthereof. The device 59 includes two substantially cylindrical portions61 and 62 spaced from each other by protuberances preferably on theinner side of cylinder 61. This provides a multiplicity of passageways63 between portions 61 and 62. It will be noted that the cylinder 62 is]spaced at its lower end from the angular extension 64, which extendsfrom the lower portion of cylinder 61, to form an opening 65 betweenextension 64 and cylinder 62.

The upper ends of cylinders 61 and 62 terminate in angular portions 66and 67. A horizontal portion 68 extends from the angular portion 66. Atop 69 is mounted above the horizontal portion 68 to provide a passage70 therebetween. An opening 71 is formed between the spaced angularportions 66 and 67. The feed control device 59 is supported from thetube 58 by means of flanged member 72. The bottom of the refrigerantreservoir is indicated by member 73.

Liquid refrigerant enters through the feed hole 69 and fills up theportion of the device 59 surrounding the tube 58 until the level in thedevice 59 reaches the .4 top of the tube 58 when liquid refrigerantbegins to flow over the lip of the tube and wet the inner surface of thetube. The vapor generated from the liquid refrigerant being evaporatedin tube 58 will flow upwardly through cylinder 62 to passage 70. Thearea of the passage 70 in the vicinity of opening 71 is smaller in crosssection than the area of the tube 58 so that the velocity of the vaporin passage 70 is greater than in cylinder 62 and the static pressure inpassage 70 is less than at the upper exit of tube 58.. Therefore, thisvapor will tend to cause the liquid to rise in passages 63. and beentrained with the vapor in passage 70 by escaping through the opening71 formed between the portions 66 and 67 continuing on through anopening (not shown) to the vapor header. By selecting the area ofpassage 70 and the distance between the top of the tube 58 and thehorizontal portion 68, the desired amount of flow of liquid refrigerantto the tube may be regulated.

Figure 4 illustrates another form of the invention wherein an outercasing 30, similar to member 61, is provided with a substantiallycylindrical central body portion 31 provided with a series ofcircumferentially spaced, axially extending grooves 32, and a flared endponiton 33 terminating in a substantially horizontal end portion 34. Thecasing is further formed with an inwardly extending foot 36 havingspaced apertures 37 therein, and a tube engaging portion 38 extendingaxially of the casing and spaced inwardly of the body portion 31, theportion 38 terminating in a flange 39 adapted to engage the end of thetube to support the regulating device in suspended position thereon.

The material from which the casing is fabricated is preferably sheetmetal so as to respond readily to conventional stamping and formingoperations. Attached to the portion 34 at circumferentially spacedlocations are a series of axially extending resilient tabs 40 havinghooked end portions 41.

Assembled within the outer casing 30 is an inner member 42 having asubstantially cylindrical portion 43 and a flared end portion 44integrally connected thereto. The outer surface of the inner member mayfrictionally engage the projections formed by the grooves 32 or it maybe secured to the projections by welding or some equivalent operation.When assembled in the manner described a series of chambers 45 similarto passages 63, are provided having a lower end, communicating with areservoir 46 formed by the tube engaging foot and inclined portion ofthe casing, and an open upper end.

The regulating device is further provided with a cover 47 arranged tohave spaced marginal portions frictionally engaged by the hooked endportions of the resilient tabs 40. Thus it will be noted that a seriesof outlets are formed in the top of the regulating device. The centralportion of the cover is dished inwardly so that when assembled with themembers 30 and 42 as shown in Figure 4 a passage 48 for the flow ofvapor is provided. The passage is characterized by a first section 49having a relatively large cross sectional area and a portion 50 the axisof which extends substantially normal to the axis of portion 49. Thecross sectional area of the portion 50 is smaller than the crosssectional area of the section 49.

Considering the operation of the flow regulating device 59 or 30, oncethe refrigerating effect to be produced by each tube has been determinedby considering the rate of refrigerant flow in the system, the amount ofheat exchange desired, the vapor flow occurring in relation to theliquid refrigerant feed per tube, then the dimensions of the individualsections of the device are calculated' so that the vapor flowingupwardly in the tube will be under a certain velocity and staticpressure in the lower part of the passage, and because of reduced areaofthe upper part of the passage, be under a lower static pressure andhigher velocity. The area of low pressure will be in communication withthe upper opening of the chamberca'using a part of the'liquid in thereservoir to rise in the chamber and be entrained in the vapor emanatingfrom the regulating device. The entrained liquid will then drop bygravity into the header and flow through openings 37 into the bottom ofthe reservoir from where it flows either downwardly through the tube tobe vaporized therein or upwardly into the chamber defined by the innerand outer member; I

It will be obvious that when the design conditions are fulfilled theflow of liquid refrigerant into the evaporator tube will beefiectivelycontrolled so that the level to which the refrigerant flowsdown the surface may be determined and minor leveling misalignments willonly serve to cause the level to vary within minor limits.

Variations in the system operating conditions may be consideredinconsequential once the design of the regulating device installed onthe top of each evaporator tube is properly made and the proper solutionconcentration control means are provided in the cooperating absorptionrefrigeration system.

For example, if the load on the evaporator is reduced temporarily as aresult of cooler air flowing over the outside of the tubes, the vaporflow through the feed control device will also reduce temporarily and anexcess of refrigerant will flow into the tubes.

By means known to the art, this excess refrigerant, which will notevaporate and will run out the bottom of the evaporator tubes, iscollected and segregated from the absorbent solution circulating system.This causes increased concentration of the solution in the system andparticularly in the absorber. Lower pressure results in the evaporatorand consequently an upward adjustment of the vapor flow rate from theevaporator tubes occurs until each tube is producing close to the designvalue. The refrigerant is then again properly divided between thevarious tubes of the evaporator as before.

It should be borne in mind that the small absorption units in which thedisclosed device is used are essentially fixed capacity machines withthe total quantity of refrigerant condensed and evaporated dependinglargely on the fixed amount of heat supplied to the generator component.

Summarizing, it will be evident that the flow in each tube will becontrolled in part by the vapor flow which is directed in a manner toinduce portions of the liquid to be entrained therewith. The degree ofliquid entrainment by the vapor flow will of course be dependent uponthe relative dimensions of the differential passageway 48. Thus adesired volume of liquid flow upwardly through the receptacle may beobtained by varying the dimensions of the passageway. Other structuralarrangements may be employed in the practice of this invention withoutdeparting from the spirit of the invention. For example, the outermember 31 or 61 and the cover 69 or 47 may be formed from a piece oftubing, having one end closed and the openings, permitting the flow ofvapor to emanate from the device, placed therein.

Although only two forms of the invention have been described it will beobvious that other structural arrangements illustrating the inventionwill suggest themselves to those skilled in the art without deviationfrom the spirit or scope of the invention as defined in the claims.

I claim:

1. A device for regulating the supply of liquid to an evaporator tubecomprising an outer member supported from and surrounding the top of thetube, said outer member including an apertured portion disposed belowthe top of the tube serving as a reservoir for liquid refrigerantintroduced through the aperture; an inner member assembled within theouter member and in spaced relation to portions of the outer member soas to form at least one passage in communication with the reservoir; anda cover mounted in spaced relation to the top of the outer member, andforming with the inner member, a passage for the flow of vapor from thetube, said passage having a first section in communication with thetube, and a second v. 6 section having across-section smaller than thefirst sec tion whereby vapor flowing in the second section induces aflow of liquid into the passage from the reservoir.

2. A receptacle for the supply of liquid refrigerant to an evaporatortube comprising an outer member having a base, an upwardly'extendingmarginal wall, a tube engaging flange spaced from the base, a wallconnecting the base and the flange, said base being provided with aseries of openingsfor the introduction of liquid into the space definedby the walls; an inner member assembled in spaced relation tothemarginal wall of the outer member to form a chamber'therewith, saidinner member termi nating above the tube engaging flange; and a covermember mounted in spaced relation to the upper part of the outer member,the parts being arranged to provide a passage for vapor flow from thetube, said passage being characterized by a first section in axialalignment with the tube and a second section of reduced dimensionsradiating from the first portion so that the velocity of the vapor flowis increased as it flows from the receptacle to induce the flow ofliquid upwardly in the chamber.

3. A receptacle of the type described in claim 2 wherein said covermember is provided with a circumferentially interrupted skirt portion.

4. A receptacle of the type described in claim 2 wherein said outermember is provided with at least one extension for supporting the covermember.

5. A receptacle of the type described in claim 2 wherein the centralportion of the cover is dished inwardly in the direction of theevaporator tube.

6. An absorption refrigeration system comprising a generator, acondenser, an absorber, an evaporator including a liquid refrigerantaccumulating header and at least one evaporator tube, a solution pumpfor forwarding a solution of refrigerant and an absorbent to thegenerator from the absorber, conduits interconnecting the generator,condenser, absorber and evaporator whereby vaporous refrigerant formedin the generator is condensed and forwarded to the evaporator to bevaporized therein from where it flows to the absorber to be absorbed bythe solution returning from the generator to complete the refrigerationcycle, and means for controlling the flow of liquid refrigerant to theevaporator tube, said means including a tube engaging member having anapertured reservoir extending below the liquid level in the evaporatorheader and a passageway extending upwardly from the tube so arranged tocause vaporous refrigerant to entrain from the reservoir, quantities ofliquid refrigerant in excess of a predetermined amount.

7. A device for regulating flow of liquid into an evaporator tube of arefrigeration system to be vaporized therein comprising a substantiallycylindrical reservoirdefining member arranged to surround the top of anevaporator tube, liquid over-flowing from said reservoir into saidevaporator tube, said member having at least one opening below the levelof the top of the tube for the admission of liquid refrigerant, a secondsubstantially cylindrical member arranged within the first cylindricalmember with spaced portions thereof engaging the first cylinder to format least one passageway for the induced flow of liquid refrigerant forreturn to the absorber, said induced flow being under the influence of aflow of vapor from the evaporator tube in excess of an amount indicativeof a predetermined liquid refrigerant feed into the tube.

8. A device for regulating flow of liquid into an evaporator tube of arefrigeration system to be vaporized therein comprising a substantiallycylindrical reservoirdefining member arranged to surround the top of anevaporator tube, liquid over-flowing from said reservoir into saidevaporator tube, said member having at least one opening below the levelof the top of the tube for the admission of liquid refrigerant, a memberhaving a wall portion forming with the reservoir-defining member apassageway for the induced flow of liquid refrigerant for return to. theabsorber, said induced flow being under the. influence, of a flow ofvapor from the evaporator tube in excess of an amount indicative of apredetermined liquid refrigerant feed into the tube. V

9. A device for regulating the flow of liquid into an evaporator tube ofa refrigeration system to be vaporized therein comprising means foraccumulating a quantity of liquid adjacent the top of the tube so thatthe liquid spills. over thetopof the tube, and means utilizing vaporousrefrigerant formed in. the tube for diverting from the accumulatedliquid a quantity of the liquid in excess of an amount required tomaintain a desired rate of flow,

said las me t oned m an i i u hlg a eceiver pro i ed w th a. d ffe en ip sage fo th flow ofvapors from the tube.

References Cited in thefil Of this patent UNITED STATES. PATENTS2,408,480 Reid Oct. 1, 1946, 2,465,904- McNeely Mar. 29', 1949 2,563,574Berry Aug. 7', 1951 2,740,263 Kritzer Apr. 3, 195,6

